The present invention relates to an electromagnetic-wave shielding and light transmitting plate which has excellent electromagnetic-wave shielding characteristics, near infrared ray blocking property and optical transparency and, more particularly, to an electromagnetic-wave shielding and light transmitting plate suitable for a front filter of a PDP (plasma display panel). Further, the present invention relates to a display device, such as a PDP, having the electromagnetic-wave shielding and light transmitting plate.
With the spread of electronic appliances including office automation apparatuses and communication instruments, electromagnetic wave emission from these appliances has come into a problem. That is, adverse effect of electromagnetic wave to the human body is feared and it is also a problem that the electromagnetic wave affects a precision apparatus to cause malfunction.
For this, plates having good electromagnetic-wave shielding function and still having light transparency have developed as front filters for PDPs of the office automation apparatuses and come into commercial use. Such plates are also used as windows of a place where a precision apparatus is installed, such as a hospital or a laboratory in order to protect the precision apparatus from electromagnetic waves from a portable telephone.
A conventional electromagnetic-wave shielding and light transmitting plate typically comprises transparent base plates such as acrylic boards and a conductive mesh member like a wire netting and is formed by interposing the conductive mesh member between the transparent base plates and by assembling them.
An electromagnetic-wave shielding and light transmitting plate, which has improved characteristics and allows easier handling as compared with the conventional one, is disclosed in Japanese patent publication H11-74683A in which a conductive mesh member is interposed between two transparent base plates and integrally bonded together by transparent adhesives.
This electromagnetic-wave shielding and light transmitting plate has good electromagnetic shielding capability and has light transparency so that distinct pictures are displayed. Further, it has the conductive mesh member interposed between the transparent base plates, thereby preventing scattering of fragments of the transparent base panels when damaged.
In order to improve the electromagnetic-wave shielding function in the conventional electromagnetic-wave shielding and light transmitting plate, it is necessary to ground or earth the electromagnetic-wave shielding member, e.g. the conductive mesh member to the PDP body. Accordingly, the electromagnetic-wave shielding member should extend out of the transparent base plates which interpose the shielding member therebetween so that an extended margin of the shielding member is bent toward and grounded at the back of the assembled light transmitting plate or, alternatively, a conductive adhesive tape should be interposed between the two transparent base plates to come in contact with the electromagnetic-wave shielding member. Typically used as a transparent base plate is a glass plate having a thickness of 2-3 mm. Accordingly, when used for a filter for a big screen, such a glass plate should be considerably heavy so that it is not only hard work to laminate the base plates but also difficult to secure such laminating work.
The electromagnetic-wave shielding and light transmitting plate using two transparent base plates has a great thickness and a heavy weight. It is desired to reduce the thickness and weight of the electromagnetic-wave shielding and light transmitting plate.
In order to prevent malfunctions of remote controllers, the electromagnetic-wave shielding and light transmitting plate requires to prevent near infrared ray from transmitting therethrough. Since the brightness of PDPs has been enhanced, the amount of near infrared rays generated from such PDP increases. Therefore, it is required to impart further improved near infrared ray blocking function.
A transparent base plate made of acrylic resin containing copper material has excellent near infrared ray blocking function. However, acrylic resin has a problem about heat resistance, that is, has poor heat resistance and may be easily thermally deformed. Therefore, it is desired to provide an electromagnetic-wave shielding and light transmitting plate with improved near infrared ray blocking function by using glass base plates having excellent heat resistance as transparent base plates. In addition, when using acrylic resin plates as transparent base plates, it is desired to further improve the near infrared ray blocking function.
It is a first object of the present invention to solve the aforementioned problems and thus to provide an electromagnetic-wave shielding and light transmitting plate which solves the aforementioned problems, is suitably used for an electromagnetic-wave shield filter for a PDP, is thin and light, has excellent durability, has excellent electromagnetic-wave shielding function and improved near infrared ray blocking function, and still has high transparency in a range of visible light, thereby displaying distinct pictures.
It is a second object of the present invention to provide an electromagnetic-wave shielding and light transmitting plate which facilitates the work for laminating filter components, and which has excellent electromagnetic-wave shielding function and impact resistance (hard to be broken).
It is a third object of the present invention to provide an electromagnetic-wave shielding and light transmitting plate with a near infrared ray blocking film having improved resistance to heat, moisture, and ultraviolet ray.
It is a fourth object of the present invention to provide a display device which has the electromagnetic-wave shielding and light transmitting plate mentioned above.
The electromagnetic-wave shielding and light transmitting plate of the present invention has a transparent base plate, an electromagnetic-wave shielding member, an antireflection film as the front-most layer, and a near infrared ray blocking film which are laminated and integrated together. The near infrared ray blocking film has a base film and a near infrared ray blocking layer formed on a surface of the base film. The near infrared ray blocking layer contains a near infrared ray absorbing agent composed of diimmonium compound, and further contains a copper complex having the following formula (A) and/or a copper compound having the following formula (B): 
The near infrared ray blocking film to be used in the electromagnetic-wave shielding and light transmitting plate of the present invention contains the diimmonium compound as the near infrared ray absorbing agent in the near infrared ray blocking layer, and contains the aforementioned copper complex and/or the copper compound are employed as the antioxidant agent in the near infrared ray blocking layer, so that the near infrared ray blocking film has significantly improved resistance to heat, moisture, and ultraviolet ray. Therefore, the near infrared ray blocking film keeps its near infrared ray blocking efficiency for a long period of time at a high temperature.
In the base polymer of the near infrared ray blocking layer, the diimmonium compound and the copper complex and/or the copper compound are dispersed. It is preferable that the amount of the diimmonium compound in the near infrared ray blocking layer is 0.01 to 100 parts by weight relative to 100 parts by weight of base polymer and the amount of the copper complex and/or the copper compound in the near infrared ray blocking layer is 0.01 to 100 parts by weight relative to 100 parts by weight of the diimmonium compound.
It is preferable that the base polymer is acrylic resin or polyester resin and the base film is a polyester film.
The antireflection film may be disposed at the front-most side of the electromagnetic-wave shielding and light transmitting plate and the near infrared ray blocking film is disposed at the rear-most side thereof. Both surfaces of the transparent base plate covered by these films improve the durability of the transparent base plate and provide an effect of preventing the transparent base plate from scattering even if broken. Furthermore, work for grounding or earthing the electromagnetic-wave shielding member to the PDP body can be facilitated, thereby ensuring this work without mistake.
It is preferable that the electromagnetic-wave shielding member is a mesh member made of metallic fibers and/or metal-coated organic fibers. Use of this conductive mesh member provides an effect of preventing the scattering of fragments when damaged and thus improving the safety.
In the electromagnetic-wave shielding and light transmitting plate of the present invention, the transparent base plate, the respective films, and the electromagnetic-wave shielding member are bonded and integrated by transparent adhesives. Use of transparent elastic adhesives as the transparent adhesives further ensures the effect of preventing the scattering of fragments when the plate is damaged due to impact or the like.
The transparent adhesives may contain ultraviolet ray absorbing agent, whereby the electromagnetic-wave shielding and light transmitting plate has further improved ultraviolet ray resistance.
The display device of the present invention has the electromagnetic-wave shielding and light transmitting plate of the present invention.